The risk of sudden death for infants could be doubled by mothers smoking cigarettes during pregnancy, even with only a single cigarette each day, according to a new study. At a pack a day, that risk triples.

More than 20 million births were used in the study, including 19,000 infant deaths, in data from the US Centers for Disease Control from between 2007 and 2011. It showed a 0.07 increase in the odds of sudden infant death with each cigarette smoked daily. The study was published Monday in the journal Pediatrics.

Despite the risk associated with relatively light smoking, the study shows that throughout pregnancy, cutting down can help minimize the risk, according to CNN. The study found a 12 percent decrease in sudden death risk for women that reduced their smoking by their third trimester, and a 23 percent difference for those that quit smoking completely by the third trimester.

“Every cigarette counts,” according to the study’s lead author, Seattle Children’s Research Institute neuroscientist Tatiana Anderson. “And doctors should be having these conversations with their patients and saying, ‘Look, you should quit. That’s your best odds for decreasing sudden infant death. But if you can’t, every cigarette that you can reduce does help.”

Sudden unexpected infant death (SUID) includes three categories of infant deaths. Sudden infant death syndrome, or SIDS, refers to a category of sudden deaths that remained unexplained for decades. Researchers ultimately found it was common in babies that were put to sleep laying on their stomachs.

Starting in the mid-1990s, education programs encouraging parents to put babies to sleep on their backs, and to remove clutter from the sleeping area, reduced SIDS rates by more than half by 2010.

But in the same period, sudden deaths from accidental suffocation and other ill-defined causes increased. The SUID category encompasses all three categories.

Researchers have found links between smoking during pregnancy and SUID. With SIDS, as many as a third of cases are linked to smoking. Even secondhand smoke leads to a 20 percent increased risk of low birth weight.

Researchers are investigating the nature of the connection between a mother’s smoking and SUID. One theory is that by increasing levels of the neurotransmitter serotonin, it could affect an infant’s ability to regulate its respiratory system while asleep.

Smoking rates have declined in the US, but according to self-reported surveys, about 338,000 women smoke during pregnancy each year.

According to Anderson:

“These numbers are probably on the conservative side. Women know they shouldn’t be smoking during pregnancy, and there is a certain population that either denies that they smoke or underestimates the number of cigarettes they smoke.”

If all women stopped smoking during pregnancy, the study’s models estimated that about 800 infant deaths would be prevented annually.


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